The present invention relates to anti-vibration mounts intended to be interposed between two rigid elements to damp vibrations between these two elements essentially on a central axis, this mount comprising:
an elastomer body substantially centered on the central axis,
a rigid base fixed to the elastomer body and including a periphery surrounding said elastomer body, this periphery extending substantially in a plane perpendicular to the central axis,
a rigid head fixed to the elastomer body and offset from the base along the central axis, and
at least a first non-extensible cable formed as a loop, which is fixed to the base and to the head to limit the distance between said base and said head, the cable comprising a first part supported on the head by winding around it and extending towards the base from said head.
Limiting cables of this kind which are currently in use are generally formed by non-extensible cables wound around anti-vibration mounts in a plane parallel to the central axis. The document EP-A 0 518 759 describes an example of an anti-vibration mount including such a limiting cable.
The disadvantage of cables of this type lies in the fact that when the mounts are of large dimensions the cables themselves must be of large dimensions and, furthermore, of sufficient strength. In this case the cables require a large amount of material for their manufacture, making them relatively expensive.
Another disadvantage of these cables is that they reduce the portions of the support surfaces of the anti-vibration mounts which allow the mount to be connected between the two rigid elements. Thus the fatigue strength of, especially the caps which may form one of the support surfaces of these anti-vibration mounts is diminished.
U-shaped limiting cables intended to surround only one part of the anti-vibration mounts also exist. For this purpose they comprise a central section attached to the head of the mount, the two free ends of the central section being fixed to diametrically opposed portions of the base of the mount. However, these cables are not satisfactory, as there is a risk that their free ends may become detached from the base through tearing out of the ferrule crimped or cast on to the said free ends, and/or by the rupture of the areas of the base to which these ferrules are attached.
A primary objective of the present invention is to remedy the above-mentioned disadvantages of anti-vibration mounts with limiting cables forming a loop, without incurring the disadvantages of the U-shaped limiting cables.
To this end, an anti-vibration mount of the kind in question, with a limiting cable forming a loop, is characterized essentially in that it comprises a second part which is arranged along at least a first portion of the periphery of the base, said second part complementing the first part of the first cable to constitute said loop formed by the first cable, the first cable thus being wholly comprised between the periphery of the base and the head,
and in that the second part of the first cable winds around at least a first return element forming part of the periphery of the base, level with two joints between said second part and the first part of the first cable, the first cable being restrained by the first return element in such a manner that said first return element prevents any displacement of the second part of the first cable towards the head.
Thus, the cable surrounds the anti-vibration mount on only one part of its height, so that the part of the mount situated opposite the head can be left completely free, this part being able to be formed, in particular, by a rigid cap fixed to the base.
In preferred embodiments of the invention, one or more or the following arrangements might also be used:
the second part of the first cable extends in a plane substantially perpendicular to the central axis;
the two joints between the first and second parts of the first cable are contained respectively within first and second intersecting planes which pass through the central axis and form an included angle of between about 90xc2x0 and about 180xc2x0;
the angle between the first and second intersecting planes is of between about 160xc2x0 and about 180xc2x0, so that the first part of the first cable extends in a plane substantially parallel to the central axis and adjacent to this central axis;
the first part of the first cable extends in a plane forming an acute angle with the central axis;
the first cable is formed in one piece;
the first cable comprises, about the middle of its second part, two free ends which are connected together by a connecting means; thus, the free ends of the first cable, which are arranged in a manner sufficiently far from the stressed zones of the base, are subjected only to weak traction stresses, a large part of the traction stresses being absorbed by friction between the first cable and the periphery of the base;
said first return element is formed by a rigid, fixed projection;
the first cable is held in position in relation to the mount by retaining means;
the retaining means are formed by an elastically deformable strap having two ends integrated with the first cable in the vicinity of the two joints between the first and second parts of the first cable respectively, this elastically deformable strap being arranged around a second portion of the periphery of the base, this second portion being complementary to the said first portion of the periphery of the base;
the retaining means include at least two second return elements which are arranged in a fixed position on the periphery of the base, in the vicinity of the two joints between the first and second parts of the first cable respectively, and extending outwardly in two opposite directions, the second part of the first cable winding between the first and second return elements along a sinuous path;
the retaining means include at least two third return elements which are arranged in a fixed position on the periphery of the base, in the vicinity of the second return elements respectively, and extending outwardly in two opposite directions, the first part of the first cable winding between the second and third return elements along a sinuous path;
the periphery of the base is provided with two first return elements which extend outwardly in two opposite directions respectively, said first part of the first cable being supported on said first return elements level with each of its two joints with said second part of the first cable respectively;
a second non-extensible cable, analogous to the first cable, is fixed to the base and the head opposite to the first cable.